Strapping machine



May 23, 1967 R. L. GASPER ET AL 3,320,874

STRAPPING MACHINE Filed Sept. 27, 1965 8 Sheets-Sheet 1.

Z320@ i faz/)L 62g @2 im@ 9%@ df@ May 23, 1967 m.. GASPER ETAL 3,320,874

STRAPPING MACHINE Filed Sept. 27, 1965 8 Sheets-Sheet 2 May 23, 1967 R, GASPER ET AL STRAPPING MACHINE 8 Sheets-Sheet 3 Filed Sept. 27, 1965 May 23, 1967 R L, GASPER ET AL 3,320,874

STRAPPING MACHINE 8 Sheets-Sheet 4 Filed Sept. 27, 1965 May 23, 1967 R. L GASPER ET AL 3,320,874

STRAPPING MACHINE FledSept. 27, 1965 8 Sheets-Sheet 5 May 23, 1967 R. L `GASPER ET AL STRAPPING MACHINE 8 Sheets-Sheet 6 Filed Sept. 27, 1965 May 23, 1967 R, L, GASPER ET A1. 3,320,874

4 STRAPPING MACHINE Filed Sept. 27, 1965 8 Sheets-Sheet 7 May 23, 1967 R. 1 GASPER ET Ae. 3,320,874

STRAPPING MACHXNE Filed Sept. 27, 1965 8 Sheets-Shleet 8 United States Patent C York Filed Sept. 27, 1965, Ser. No. 490,566 19 Claims. (Cl. 100 3) This invention relates to the art of tying cylindrical objects with binder straps and particularly relates to strapping apparatus and method for applying binder straps to for-med sheet coils.

Formed sheet coils `are mass produced in steel plants and as produced consist of a substantially tightly wound, high turn multiple spiral coil. The outer wraps of the coil, however, are loose because of the natural unwinding tendency of any formed sheet coils and the problem is to tighten the loosened outer wraps and apply a strap loop snug on the tightened coil. In the usual steel production operations, these coils are hot when presented for tying at the strapping station. The wrap tightening and coil tying problem is greatly aggravated by the heated condition of the coils.

In production line operations, the coils to be tied are advanced in succession to the strapping station and exact alignment of the coil center line wit-h the strapping head is diicult to assure but is important in facilitating the strapping operation.

Until now, it has been difficult to tie a coil with a strap loop except by tolerating some looseness in the outer wraps of the coil. Arrangements to accomplish wrap before application of the strap loop have been trieda but the installation is greatly complicated and the wrapping equipment is subject to excessive wear and maintenance. Arrangements to insure exact centerline registry are known but the equipment is complicated and expensive.

The principal object of the invention is the provision of improved strapping apparatus for tying a loop of a binder strap about a cylindrical object.

Another object of the invention is the provision of improved strapping apparatus having means for maintaining required tangency between a strapping head and a cylindrical object which is to be tied with a binder strap by the action of the head.

A further important object of the invention is the provision of improved strapping apparatus and method for tying a binder strap loop in tight relation about a formed steel coil.

Still another object of the invention is lthe provision of novel apparatus and method for wrapping and tying a formed coil by establishing a strap loop snug upon the outer wrap and rotating the loop and outer wrap in a coil wrapping movement to draw the inner wraps taut while taking up strap to shrink the strap loop and outer wrap as the coil shrinks.

The technique of using the strap loop as the coil gripping element during the wrapping action enables direct transition from coil wrapping to strap loop tyingy and sealing; permits faster total operating time since wrapping and final strap loop tightening occur simultaneously; enables only the particular single use strap loop to take all the wear associated with contacting the hot coil while providing a wrapping action which minimizes marking or damaging of the outer wraps of the coil; avoids strict dependence upon exact registry of the coil centerline and the strapping head; and permits the strapping head and its support structure also to apply the wrapping force, thus obviating necessity of other powered devices for performing the wrap function. Another object of the invention is to provide 'a strapping apparatus and method exhibiting these advantages.

A further specific object of the invention is the provision of strapping apparatus having positioning linkage for powering a strapping head through an arcuate wrapping path while maintaining tangency of the strapping head to the coil periphery.

Another object of the invention is the provision of a strapping apparatus for final wrapping and tying of coils on a production line, with the apparatus being functional for wrapping in opposite directions to enable ease of f adaptation to any type of production line.

Still a further object of the invention is the provision of strapping apparatus and method particularly suited t0 wrapping and tying a hot formed coil. by establishing a strap loop snug on the coil an slowly rotating the loop to wrap the coil while adjusting loop size, with the loop expansion due to thermal effects being automatically cornpensated.

Other and further objects of the present invention will be apparent from the following description and claims, and are illustrated in the accompanying drawings which show structure embodying preferred features of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles.

In the accompanying drawings forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same;

FIG. 1 is a perspective View of a strapping station of a type used in conjunction with a production line for hot formed steel coils, the station being equipped with a strapping head mounting 'and positioning system in accordance with the present invention;

FIG. 2 is a side elevational View of the strapping head and positioning system;

FIG. 3 is a plan view of the positioning system structure of FIG. 2;

FIGS. 4, 5, and 6 are fragmentary sectional views taken as indicated by the lines 4 4, 5 5, and 6 6, respectively, on FIG. 3;

FIG. 7 is a plan view of a strapping head and a strap guide segment;

FIGS. 8, 9, and 10 are diagrammatic plan views of the positioning system of FIG. 3;

FIG. 11 is another diagrammatic plan view of the positioning system;

FIG. l2 is a hydraulic circuit diagram; and

FIG. 13 is an electric circuit diagram.

The invention is described in association with a production line of formed hot steel coils and the strapping station may have the general arrangement shown in Winkler Patent No. 3,252,408, issued May 24, 1966.

The principal features of the strapping station are described here to provide proper environment for understanding the operation of the strapping system of this invent but it should be understood that the present system has application apart from the specific arrangements shown herein.

The strapping machine 1 in which the invention is shown embodied consists of two bases 2 and 3; the ibase 2 supports two corner posts 4 and 5 while the base 3 supports two corner posts 6 and 7. An I-beam 8 is connected between the upper ends of the two posts 4 and 5 while another I-beam 9 is connected -across lthe upper ends of the two posts 6 and 7. Mounted between the posts 4 and 6 at the upper ends is another I-beanr 10. Similarly mounted between the posts 5 and 7 at their upper ends is another I-beam 11. The carriage 12 is mounted for vertical movement between the posts 4 and 5 and is supported by two chains 13 and 14 which are driven by means of sprockets at attached to a shaft 16. Likewise, a carriage 17 is mounted for vertical movement between the two posts 6 and 7 and supported by means of two chalns 1S and 19 driven by means of two sprockets at 2t) secured to the shaft 16. The shaft 16 is driven in one direction or the other by means of a motor 21 suitably mounted 'on a platform 22 secured t-o the post 7.

The chains 13 and 14 are connected at their opposite ends to a counterweight 23 which is guided along the post 5. In a similar manner, t-he Opposite ends of the chains 18 and 19 are secured to another counterweight 24 guided along the corner post 7. With this arrangement, rotation of the shaft 16 by the motor .21 in one direction causes both carriages 12 and 17 to be lowered together while rotation of the shaft 16 by the motor 21 in the opposite direction causes both carriages 12 and 17 to be elevated.

The carriage 17 supports a strapping head 25 mounted on a horizontal slide carriage 26 which is mounted for movement toward and away from the object to be strapped on the two end plates 17a and 17h of the carriage 17. The strapping head 25 can be of many types, but one particularly suited for such a structure is shown in United States Letters Patent No. 3,120,171, which issued on Feb. 4, 1964, in the names of Sidney V. Hettinger, Jr., and Marchand B. Hall. Such a strapping head automatically feeds a length of strap from a supply source (not shown), permits the length of strap to be encircled into a strap loop, automatically shrinks the strap loop onto an object, and secures the overlapping ends of the strap loop together and severs the strap loop from the supply source.

A strap guide segment 27 carried on the strapping head 25 is positioned vertically by movement of the carriage 17 and a corresponding strap guide segment 30 is positioned vertically by movement of the carriage 12. The carriages 12 and 17 move in synchronism between an upper position wherein the strap guide segments 27 and 30 are in a common horizontal plane with strap guide segments 28 and 29 and a lower position which is pictured in FIG. 1.

When the carriages are in their upper position, adjacent ends of the guide segments 27, 28, 29, and 30 are aligned and cooperably define a generally circular continuous path guideway beginning and ending at the strapping head 25. The strapping head 25 is operable to feed strap through this guideway to form a closed loop or strap S at this elevated position.

The object to be strapped, which is here represented asa hot formed steel coil 31, may be advanced to the strapping station on a horizontal conveyor 32 while the carriages 12 and 17 are at their upper position and the strapping head 25 is forming a closed loop or strap. The coil 31 is brought to a position of approximate registry at the strapping station to be within and below the peripheral outline of the strap loop.

When the coil is in proper position, the carriages 12 and 17 descend to lower the loop of strap S to the position illustrated in FIG. 1 to encircle a midheight region of the coil. The guide segments 27, 28, 29 and 30 are preferably constructed and operated as described in the aforesaid Winkler Patent No. 3,252,408. Thus, before the carriages are lowered to cause the strap guide segments 27 and 30 to also be lowered, the strap guide segments 28 and 29 must be clear of the loop of strap S. Then as the loop of strap is tightened and shrunk onto the coil 31, it must be free to pull out from the confines of the strap guide segments 27 and 30. During this action, progressively less support is provided from the guide members 27 and 30. To prevent drooping of the loop of strap and consequent improper location on `the coil, a pair of strap support arms 34 (only one of which is shown) are pivoted to the carriage to swing in a horizontal plane and contact portions of the coil during shrinkage of the loop of strap. Concurrently, the strapping head 25 is moved towards the coil and is guided by and mounted on the horizontal slide carriage 26 in a fashion to generate and apply a wrapping action on the coil.

The structural details of the horizontal slide carriage 26 are shown in FIGS. 2 to 7 and the principles and features of its action in facilitating wrapping of a hot formed steel coil that may have loose outer wraps are diagrammed in FIGS. 8, 9, and 10. The adaptability of the arrangement to compensate for lack of regis-try of the coil as delivered on the conveyor 32 is illustrated in the diagram of FIG. 11.

It is useful to describe the general principles of the invention for effecting a tight wrapping of the coil 31. This is accomplished by moving the strapping head 25 through a prescribed pat-h and maintaining a prescribed orientation with respect to the coil periphery 31P. The operation of the strapping head 25 is controlled in relation to its travel path to draw the strap loop snug on the outer wrap of the `coil where the strapping head is at one extreme of movement along the coil periphery, to enable the strap loop to wrap the coil tight by rotating as a capstan and shrinking in size as the head moves in a wrapping direction along the coil periphery and maintains tension by taking up slack as the wrapping action reduces the outer diameter of the coil, and to enable sealing of the strap loop when the head is at the point where the coil is fully wrapped.

The general path of movement of the strapping head maybe traced with reference to FIGS. 8, 9, and 10. The horizontal carriage 26 rst moves the head mounting plate 25M directly towards the coil periphery as illustrated in FIG. 8. A novel linkage system then moves the head mounting to the start position which represents one extreme of movement of the head along the coil periphery. At this point, the head plate 25M and hence the head 25 are in tangency to the coil periphery and tension is drawn to bring the loop snug and tend to rigidify the outer wrap of the coil 31. The head 25 is now moved in a wrapping direction (indicated by the arrow W in the drawings) along the coil periphery to move from the FIG. 9 position towards the FIG. l0 position, with the head being maintained tangent to the coil periphery. This wrapping movement is applied to the outer wrap of the coil by the gripping action of the revolving strap loop S, and as the wrapping action tightens the coil and reduces its diameter, the head pulls the strap to maintain a snug grip of the loop on the shrinkage outer wrap. The wrapping movement will stall when the coil is tight, usually before the opposite limit position of movement is reached.

The actual wrapping stroke may be completed in less than 4 or 5 second-s but final sealing of the strap loop is timed to occur only after a certain interval (4 or 5 seconds in this example) which is selected to allow completion of a maximum length wrapping stroke and also to allow for full thermal expansion of the strap loop due to contact with the high temperature coil. When the preselected interval times out, proper tension will already exist on the strap loop and the opposite ends of the loop are sealed and the `supply end severed to free the head of the coil.

The head 25 now returns vto the FIG. 8 position and the horizontal carriage 26 thereafter retracts. When the carriage 26 is fully retracted, the main carriages 12 and 17 are raised to elevate the entire mechanism to its upper position wherein the guide segments 27, 28, 29 and 30 are in alignment and the head 25 feeds strap to preform a loop for the next coil. The `Support arms 34 are pivoted to a retracted posi-tion and Iallow the tied coil to advance and a new coil to arrive as soon as the hea-d 25 is retracted and without waiting for full elevation of the carriages 12 and 17.

In one embodiment, such as is illustrated herein, the strapping station equipped with .a head movement and positioning system of this invention can handle wrapping and tying of coils of any diameter within a range of 36 inches to 72 inches. In the diagram of FIGS. 8, 9 and 10, an ideal coil size of 60 inch diameter is illustrated anda maximum wrapping stroke of about 40 inches along the coil periphery is accomplished.

As is described in detail hereafter, the head movement and positioning system is automatically adaptable to the coil periphery to guide the head 25 along the coil periphery, with the head maintained tangent to the periphery. This automatic orientation of the head 25 not only adapts the equipment to coils of various different diameters but it reduces the requirement for exact registry of the center lines of the coil and the strapping station. By way of example, `for the arrangemen-t illustrated herein, a 60 inch coil can be accepted with its axis plus or minus 6 inches from the sta-tion center line and the head movement can generate a wrapping stroke of at least 24 inches along the coil periphery.

In FIG. 1l, the periphery 31P of a coil 31 is shown exactly on center; the periphery 31P is shown for a coil 6 inches IotiE center to the left and the periphery 31P is shown for a coil 6 inches on center to the right. The ease with which -such variations in center registry are accommodated should be apparent from a comparison of the corresponding head tangency positions 25, 25 and 25".

The carriage 17 which mounts the horizontal slidecarriage has `corresponding end 4plates 17A and 17B (see FIGS. l, 3 `and 7) each provided wit-h a plurality of outboard rollers 17C positioned to roll `along the vertical post members 6 `and 7 to maintain positional stability of 4the carriage 17 as it is raised or lowered by the chains 18 `and 19.

The end plates 17A and 17B are each provided with inboard rollers 17D arranged in two horizontal rows which receive and guide the side rails 26R of the horizontal slide carriage 26 and permit movement of `the carriage through Va predetermined path in a horizontal plane. As best seen in FIG. 3, the carriage 26 is stabilized by front cross brace structure 35 and rear cross brace structure 36, ea-ch connected rigidly to each of the side rails 26R. The `front cross brace structure 35 has an upstanding web 35W for strength and is provided with an arcuate ledge 35L dening a gnideway controlling the movement path of a pair of rollers 37. The rear cross brace structure 36 has an upstanding reinforcement web 36W equipped with rear bracket structure 36B that mounts a vertical pivot shaft 38 at the rear of the carriage 26.

A wrapping arm 39 extends centrally of the carriage 26 and is provided at the front with a blunt wedge shaped web portion 39W and a circular reinforcement plate portion 391 and is provided at the rear with a vertical sleeve 39S journalled on the pivot shaft 38 which defines lan axis of `swinging movement for the wrapping arm. The ledge 351. provided on the front cross brace structure has its cen-ter of curvature at the axis of the pivot shaft 33, yand rollers 37 are journalled in the web 39W to roll along the ledge SSL and support the front of the wrapping arm in wheeled engagement for free swinging movement. The rear of the wrapping ar-m 39 extends through the vertical web 36W of the rear cross brace structure 36 with sufcient clearance to accommodate required horizontal swinging movement of lthe wrapping arm.

A set of parallel positioning links 41 and 42 extend in flanking relation alongside andslightly below the wrapping arm 39. As best seen in FIGS. 3 and 6, a drive arm assembly 43 consisting of upper and lower coacting drive arms 44 and 4S, respectively, mounted on opposite ends of a vertical pivot shaft 46 journalled in the wrapping arm 39 carries a separate vertical pivot shaft 47 and 48 connected to the rear of the links 41 and 42, respectively.

A stabilizing cross arm 67 (FIG. 5) underlies the wrapping arm 39 and is rotatable on a Vertical pivot shaft 68 carried by the wrapping arm 39. The stabilizing cross arm 67 is, in turn, equipped with depending pivot shafts 69 and 70 which form pivotal connections to the links 41 and 42. The drive arms 44 and 45 together with the stabilizing cross arm 67 complete the parallel linkage system.

A tangency position sensing unit T is carried at the front of the links 41 and 42. As best seen in FIGS. 3 and 4, this sensing unit includes a separate vertical pivot shaft 49 and 50, respectively, carried at the front of each of the positioning links 41 and 42. A horizontal top support plate 51 receives the upper ends of the pivot Ishafts 49 and 50 and a bottom cross plate 52 receives their lower ends. The support plate 51 carries the head mounting plate 25M (FIG. 2). The movement of the drive arms 44 and 45 acts through the links 41 and 42 to effect swivelling movement of the support plate, mounting plate 25M and head 25 as is necessary for maintaining tangency to the -coil periphery during the wrapping stroke.

To sense tangency of the head 25, a position sensing element 53 is mounted in rotatable relation between the pla-tes 51 and 52. The sensing element 53 includes a central vertical hub 53H that is journalled on `a pivot shaft 54 which has its opposite ends carried in the plates 51 and 52. The sensing element 53 has symmetrically arranged forwardly diverging cam arms 53C radiating from the hub 53H and each carrying a cam roller 54 and 55 normally located in partially projecting relation through the open front face of the tangency sensing unit T. Finally, the sensing element 53 has a rearwardly radiating switch actua-ting arm 53A centered between a Ipair of limit switches L82() and LS21.

The centerline of rotation of the tangency sensing assembly T coincides with the center line of the sealer jaws of the head 25. When the head 25 is tangent to the coil periphery, the rollers 54 and .55 engage the coil evenly and the actuating arm 53A remains centered between the limit switches LS20 `and LS21. When the head 25 inclines a predetermined extent from tangency in either direction, the rollers sense the change and cause the actuating arm 53A to operate a corresponding one of the limit switches for adjusting the head position through the action of the drive arms 44 and 45 and the positioning links 41 and 42.

Reference may now be had to FIGS. 3 and 12 for a disclosure of the hydraulic cylinders that operate to position the horizontal carriage 26, the wrapping arm 39, and the links 41 and 42 and plates 51 and 26M.

As shown in FIG. 12, a cylinder 56 for positioning the horizontal slide carriage 26 is selectively operated by la hydraulic solenoid valve SH2 under the control of solenoids SH2A and SI-IZB. A wrapping cylinder 57 `for positioning the wrapping arm 39 is operated by a hydraulic solenoid valve S1111 under the control of solenoids SH11A and SHIIB. A limit switch assembly 53 including `limit switches LS22, 237 24, 2S, land 28 is associated with the wrapping cylinder 57. Limit switch LSZS is shown in FIG. 13 and is closed when the wrapping `arm 39 is ahead of center while limit Iswitch LS23 is closed when the wrapping arm is beyond the center of its stroke. Finally, a head positioning ycylinder 59 is operated by a hydraulic solenoid valve SH12 under the lcontrol of solenoids SH12A and SHIZB. A limit switch assembly 60 including limit switches LS26 and LS27 iS associated with the hea-d positioning `cylinder 59.

Ars best shown in FIG. 3, the horizontal carriage cylinder 56 has its cylinder body 56B yrigidly secured to a side plate 61 at its closed front end :and rigidly secured to an inboard mounting bracket 62 carried on the side rail 26K and has its piston rod 56R anchored at its free rear end to a reaction bracket 63 carried on the end plate 17B. The wrapping cylinder 57 has its cylinder body 57B pivotally secured at its closed end to an inboard mounting bracket 64 which is xed on the other side rail 26R and equipped with a pivot pin 641 and has its piston rod 57R pivotally -secured at its free end to an upstanding pivot pin 65 carried on the reinforcement plate portion 391J of the wrapping arm 39. Finally,

the head positioning cylinder 59 has its cylinder body 59B pivotally secured at its closed end to an extension 62E of the mounting bracket 62 which is equipped with a pivot pin 621n and has its piston rod 59R pivotally secured at its free end t-o a pivot pin 63 carried on t-he upper drive arm 44.

For simplicity in illustrating the action of the linkage :structure `shown -in FIGS. 2 to 7, the elements are represented diagrammatically in a functionally similar parallel linkage system in FIGS. 8 to ll. Thus, the wrapping arm 39, the positioning links 4I and 42, the drive arm 44, the sensing element 53, the head 25, the wrapping cylinder 57 and the head positioning cylinder 59 bear the same reference characters in all of these drawings.

Sequence of operation In describing the novel wrapping technique of the present invention, it is assumed that the horizontal slide carriage 26 is at the proper desired height with respect to the coil [for locating the strap loop. It will also be assumed that the strap loop which encircles the coil has its leading end engaged by the gripping jaws of the head 25 and has its supply end extending through the tensioning wheel in the head.

Under these conditions, certain circuitry, not specilically shown in FIG. 13, receives a signal and energizes the solenoid SH2A to activate the cylinder 56 and advance the horizontal slide carriage 26 towards the coil 31. A lbumper switch LSll2 (FIGS. 7 and 13) mounted adjacent the head 25 has an activating lever arm 66 projecting forwardly and serving as the initial coil contacting element. When the slide 26 approaches the coil 31, the lever 66 operates the bumper switch LSIZ to energize relays CRS and TRIS. Since relay STR had previously been energized under the control of a limit switch LS1 (FIGURE 13) which senses the relationship of the strap loop to its guide track structure, a circuit is completed to solenoid SHIIB to control hydraulic solenoid valve SH11 and energize the `wrapping cylinder 57 for swinging the wrapping arm 39 towards its start position as illustrated in FIG. 9. This is the position for the start of the wrapping action.

It may be noted that as the wrapping arm 39 is swinging towards its start position, the horizontal slide carriage 26 is still advancing towards the coil 3l, with these combined effects maintaining the head 25 in contact with the outer wrap of the coil. Under these conditions, there is a concurrent natural motion of the linkage effecting desired head rotation for achieving tangency; however, if exact tangency is not attained, the appropriate sensing roller 54 or 55 predominates to operate either limit switch LS20 or limit switch LS21. Limit switch LS20 is connected to complete la circuit to solenoid SHIZB to operate head positioning cylinder 59 in one sense of rotation. Correspondingly, limit switch LSZI is connected to complete a circuit to solenoid SHIZA to operate head positioning cylinder 59 in an opposite sense of rotation. Thus, head position is appropriately modified under the control of limit switches L52@ and LS21 to assure essential tangency.

When the wrapping cylinder 7 has swung the wrapping arm 39 until the head actually reaches the start position illustrated in FIG. 9, limit switch LS22 closes and energizes solenoid SH3A. At this time, a circuit is also completed to a time delay relay ITR. The solenoid SH3A controls application of hydraulic power to drive the take up wheels of the strapping head in a strap tensioning direction. When the strap loop is tight to the coil, the head 25 is in effect clamped to the router wrap of the coil.

As the strap loop is fully tightened onto the coil 3l, -it is stripped from the strap guide structure associated with the head 25, thus releasing limit switch LSI and opening the circuit to relay STR. When relay STR deenergizes, its contacts 3TR4 and 3TR5 ilip-llop to de- '8 energize solenoid SHIIB and energize lsolenoid SHIIA. This reverses the action of the wrapping cylinder 57 for swinging the wrapping arm 39 in a coil wrapping direction.

Concurrently, contact 3TR3 has opened to de-energize solenoid SHZA and relieve the hydraulic vforce acting to urge the slide carriage 26 towards the coil. A limit :switch LSZS, which closed when the wrapping cylinder 57 advanced the head 25 to its start position, establishes a circuit to solenoid SHZB. Control relay CR24 has picked up when contact STRI closed and its contact CRZl-I completes the energizing circuit to solenoid SH23. Solenoid SHZB controls application of reverse hydraulic power to cylinder 56 gradually to retract the horizontal slide carriage 26.

Thus, the combined actions of the slide cylinder 56 and the wrapping cylinder 57 move the head 25 along a path on the coil periphery extending from the FIG. 9 position to the FIG. 8 position. Head tangency is maintained during such movement by the action of the sensing rollers 54 and 55 and limit switches L82@ and LS21.

The resultant force developed by the combined actions of the cylinders 56 and 57 is directed tangential tothe coil. The clamped relationship of the head 25 and the strap loop against the outer wrap of the coil provides a capstan effect in the presence of this tangential force so that the wrapping motion of the head acts to tighten the loose outer wraps of the coil.

As the coil is tightened, its circumference shrinks continually presenting an incipient slack condition tending to reduce the clamping action of the strap loop against the outer wrap of the coil. It is important in the pre.- ferred practice of the invention that the type of strapping head continuously exert a constant tensioning action to take up slack promptly as the coil size shrinks. The clamping action of the strap loop is thus maintained and the capstan action is therefore effective throughout the wrapping stroke.

As the head 25 moves from the start position of FIG. 9 and approaches the FIG. 8 position, limit switch LS28 opens to de-energize solenoid SH2B to deactivate slide cylinder 56. At this approximately normal position, the wrapping cylinder 57 can apply the wrapping force in approximately the proper direction.

If the head 25 moves beyond the FIG. 8 position, towards the FIG. 10 position, the required wrapping action has an inward component. For this purpose limit switch LS23 closes when the wrapping arm 39 moves overcenter. Limit switch LS23 closes to complete a circuit to solenoid SHZA for again moving the slide carriage 26 towards the coil 31.

Now the combined actions of the slide cylinder 56 and the wrapping cylinder 57 move the head 25 along a path on the coil periphery extending from the FIG. 8 position to the FIG. lO position. Head tangency is again maintained by the action of the sensing rollers 54- and 55 and limit switches L52@ and LS21.

The maximum possible duration of the wrapping stroke is determined by the time delay relay ITR which typically allows approximately 4 to 5 seconds from start to stop of wrap. In many instances, however, the coil is fully tightened at an intermediate stage of the wrapping cycle. In these situations, the wrapping action will stall when the coil becomes tight.

The time delay function of the relay serves two purposes. It allows the necessary length wrapping stroke and it allows the strap to come up to temperature with the hot coil before permitting sealing of the joint. When the relay ITR times out, its contacts ITK-1 and ITK-4, respectively, open to de-energize the tensioning solenoid SHSA and the wrapping solenoid SHIIA, and its contact ITK-3 energizes the sealing solenoid SH4, permitting the head to complete the seal joint and shear the strap. The sealer jaws of the head then open and free the head of the coil. The limit switch LS3A then opens to de-energze relay CR-S and its contact CRS-1 opens to deenergize relay TRIS.

The normally closed contact TRIS-2 returns to closed position to establish circuits to solenoids SH11A and SHIIB; these circuits will be selectively completed through limit switches LSZS and LSZd, depending on the position of the wrapping arm 39 at the end of the wrapping stroke. If the head 25 and wrapping arm 39 have passed through the FIG. 8 position during the wrapping stroke, LS24 will be closed and LSZS will be open; but if the head 25 has stalled before reaching the FIG. 8 position, LSZS will be closed and LSM will be open. In either event, the wrapping arm 39 is powered in the appropriate direction to return it to the FIG. 8 position. During this return travel, the contact TRlS-S establishes circuits to solenoids SHIZA and SHMB to be completed selectively through limit switches LSZQ and 21. This permits the head Z to maintain tangency during its return to neutral position. When TRIS-4 and TRIS-5 time out, LS26 and LS27 assume control of SHIZA and SH12B to bring the head to neutral position. When the head reaches neutral position and is in a tangent relationship, both limit switches LS26 and LS27 are open.

When the wrapping cylinder 57 is at its midpoint, the series connected contacts of limit switches LS24 and 25 are closed to complete a circuit to solenoid SHZB for retracting the slide 26 from the coil. After complete retraction of the slide, the entire carriage 17 is elevated until the strap guide segments 27, 28, 29 and 39 are in alignment. It is for purposes of alignment of these strap guide segments that the wrapping arm 39 and the head must be centered after completion of the strap joint.

Thus, while the preferred constructional features of the invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope Iof the appended claims.

What is claimed is:

1. The method of wrapping a spiral coil comprising, providing a strap loop in encircling relation to the coil, shrinking the strap loop into contact with the outer wrap of the coil, maintaining such contact of the strap loop while rotating the entire loop in a direction to wrap the coil tight.

2. The method of wrapping a spiral coil comprising, providing a strap loop in encircling relation to the coil, shrinking the strap loop into contact with the outer wrap of the coil, maintaining such contact of the strap loop while rotating the entire loop in a direction to wrap the coil tight, and thereafter sealing the strap loop to hold the coil tight.

3. The method of wrapping a spiral coil comprising, providing a strap loop in encircling relation to the coil, shrinking the strap loop into contact with the outer wrap of the coil, rotating the entire strap loop in a direction to wrap the coil tight while concurrently taking up incipient slack in the strap loop due to such rotation to maintain contact with the outer wrap.

4. The method of wrapping a spiral coil comprising, supporting the coil at one axial end thereof, providing a strap loop axially spaced beyond the other end thereof, producing relative axial movement therebetween to bring the strap loop in encircling relation to the coil, shrinking the strap loop into gripping contact with the outer wrap of the coil, and maintaining such gripping contact of the strap loop while rotating the entire strap loop in its own plane in a direction to wrap the coil tight.

5. The method of wrapping a spiral coil comprising, supporting the coil at one axial end thereof, providing a strap loop axially spaced beyond the other end thereof, producing relative axial movement therebetween to bring the strap loop in encircling relation to the coil, shrinking the strap loop into gripping contact with the outer wrap of the coil, and maintaining such gripping Contact of the strap loop while rotating the enl0 tire strap loop in its lown plane in a direction to wrap the coil tight, and thereafter sealing the strap loop to hold the coil tight.

6. The method of wrapping and tying a spiral coil comprising, supporting the coil at one axial end thereof, providing a strap loop axially spaced beyond the other end thereof, producing relative axial movement therebetween to bring the strap loop in encircling relation to the coil, shrinking the strap loop into gripping contact with the outer wrap of the coil, rotating the entire strap loop in its own plane in a direction to wrap the coil tight while concurrently taking up incipient slack due to such rotation to maintain gripping contact with the outer wrap, and therafter sealing the strap loop to hold the coil tight.

7. The method of wrapping and tying a spiral coil to tighten any -of its loose wraps comprising, supporting the coil at its bottom end with its axis vertical, providing a strap loop axially spaced above the other end thereof, producing relative vertical movement therebetween to bring the strap loop in encircling relation to the coil, shrinking the strap loop into gripping contact with the outer wrap of the coil, producing relative rotary movement in a horizontal plane between the coil and strap .loop in a direction to wrap the coil tight while concurrently taking up incipient slack due to such rotation to maintain gripping contact with the outer wrap, and thereafter sealing the strap loop to hold the coil tight.

8. The method of wrapping and tying a hot spiral coil to tighten any looseness in the coil wraps comprising, supporting the coil with its axis vertical, providing a strap loop axially spaced from the coil, producing relative axial movement therebetween to bring the strap loop in encircling relation to the coil, shrinking the strap loop into gripping contact with the outer wrap of the coil, producing relative rotary movement between the coil and strap loop in a direction to wrap the coil tight while Concurrently taking up incipient slack due to such rotation to maintain gripping Contact with the outer wrap, allowing sucient time for thermal expansi-on of the strap loop occasioned by its contact with the coil, and sealing the strap loop to hold the coil tight.

9. Apparatus for wrapping a spiral coil, said apparatus comprising, a strapping head having feed means for feeding strap to form a strap loop having the opposite ends of the strap loop overlapped, tension means to take up slack to tighten the strap loop, and sealing means for sealing the opposite ends of the strap loop, means for moving the head to a start position adjacent to the coil periphery in a coil wrapping direction while the tension means maintains the strap loop tight upon the coil, and means for returning the head to a strap loop forming position after the sealing means seals the strap loop tight upon the coil.

10. Apparatus for wrapping a hot spiral coil, said apparatus comprising, a strapping head having feed means for `feeding strap to form a strap loop having opposite ends of the strap loop overlapped, tension means to take up slack to tighten the strap loop, and sealing means for sealing the opposite ends of the strap loop, means for moving the head to a start position adjacent to the coil periphery where `the tension means tightens the strap loop about the coil, means for moving the head along the coil periphery in a coil wrapping direction while the tension means maintains the loop tight upon the coil, means for delaying operation of said sealing means until thermal expansion of the loop occasioned `by contact with the coil is substantially complete, and means for returning the head to a strap loop forming position after the sealing means seals the strap loop tight lupon the coil.

lll. In a system for wrapping a spiral coil by means of a -strapping head that feeds strap to form a s-trap loop having opposite ends of the strap loop overlapped, takes up slack to shrink the loop and tension the strap of the strap loop and maintains strap yloop tension, head positioning lapparatus including a carriage movable generally toward and away from the coil, a parallel arm linkage pivotally mounted on the carriage and supporting the head forwardly of the carriage, and drive means for the carriage and the linkage for moving the head adjacent to lthe coil periphery and along the coil periphery in a coil wrapping direction.

12. In a system for wrapping a spiral coil by means of a strapping head that feeds strap to form a strap loop having opposite ends of the s-trap loop overlapped, takes up slack to tighten the strap loop and tensions the strap of the strap loop and maintains strap loop tension, head positioning apparatus including a carriage movable generally toward and away from the coil, a parallel arm linkage pivotally mounted on the carriage and having a forward mount supporting the head, tangency sensing means on the mount engageable with the coil to respond selectively when the head is out of proper tangency with the coil, drive means for the carriage and the linkage, and control means connected between the tangency sensing means and the drive means for controlling the drive means to reestablish proper tangency of the head relative to the coil while moving -the head along 'the coil periphery in a coil wrapping direction .after the strap loop is tightened.

13. In a system for wrapping a spiral coil `by means of a strapping head that lfeeds strap to form a strap loop having opposite ends of the strap loop overlapped, takes up slack to tighten the strap loop and tensions the strap of the .strap loop and maintains strap loop tension, comprising, head positioning apparatus including a carriage movable generally toward and away from the coil, a parallel arm linkage pivotally mountedron the carriage and having a forward mount supporting the head, tangency se-nsing means on the mount engageaible with the coil to provide a signal when the head is out of proper tangency with the coil.

14. In a system for `wrapping a spiral ooil by means of a strapping head that feeds strap to form a strap loop having opposite ends of the strap loop overlapped, takes up slack to shrink the loop and tensions the strap of the strap loop and maintains strap loop tension, comprising, head positioning apparatus for supporting the head including a carriage movable toward and away from the coil, a head mount on the carriage, a wrapping arm aligned with said mount and supported on said carriage to rotate about an axis parallel to the axis of the coil, a positioning a-rm flanking said wrapping arm and having a forward end pivotally connected to the mount and having another pivotally connected to a drive link that is pivoted on t-he wrapping arm, and separate drive means for the carriage, the wrapping arm and the drive link cooperable for moving the head adjacent to the coil periphery and along the coil periphery in a coil wrapping direction.

15. In a system for wrapping a spiral coil by means of a strapping head that feeds strap to form a strap loop havingopposite ends of the strap loop overlapped, takes up slack to shrink the strap loop and tensions the strap of the strap loop and maintains strap loop tension until linally sealing the opposite ends of the strap loop, head positioning apparatus for supporting the head including a carriage movable toward :and away from the coil, a head mount, a `wrapping arm aligned with said mount and supported on said carriage to rotate about .an axis parallel to the axis of the coil, a pair of parallel positioning arms anking said wrapping arms and having corresponding forward ends pivotally connected to .spaced regions of the mount, and having corresponding rear ends pivotally connected to spaced regions of a drive link that is pivoted on the wrapping arm, a cross link pivotally car- -ried on the lwrapping arm forwardly of the drive link and having spaced regions pivoted to the positioning arms, drive means for the carriage, the wrapping arm and the drive link for moving the mount and the head along the coil periphery in `a coil wrapping direction, control means connected to the drive means, and tangency sensing means on the mount engageable with the coil to actuate the control means when the head is out of proper tangency with the coil, -said control means causing the drive means to urge the head into proper tangency with 4the coil.

16. Apparatus `for wrapping a spiral coilcomprising, a strap feed device for feeding a length of strap into a strap loop and positioning the strap loop circumferentially around the coil, said strap feed device being part of a head swinga'bly secured on a frame mounted for movement toward and away from the location of the coil to be wrapped, said frame Ialso being swingably mounted to direct the head in an arc along the periphery of the coil, and drive means for causing said swingably rnovement of the frame, tangency sensing means associated with the head, and control means connected between the tangency sensing means Iand said drive means for maintaining rthe `head in approximate proper tangency with the coil during the swingable movement of the frame.

17. Apparatus for strapping a cylindrical object comprising, a strapping head of a type having means for securing together the overlapping ends of la strap loop circumferentially encircled about the object, the strapping head being mounted on a frame for angular movement, reversi-ble drive means on the frame connected to selectively rotate the strapping head in either a clockwise or counterclockwise direction, a sensing means lassociated with said strapping head for contacting the peripheral surface of the object to be strapped, said sensing means being deflected one way by the surface of the object when the strapping head is at .a clockwise angle with respect to the strapping location of the surface of the object and deflected in the opposite way by the surface of the object when the strapping head is at a counterclockwise angle with respect to the strapping location of the surface of the object, said sensing means being nondeflected when the strapping head is properly tangent to the .strapping location of the surface of the object, said sensing means being connected to cause said reversible drive means to rotate the strapping head counterclockwise when the sensing means is deflected said one way and to cause said reversible drive means to rotate the strapping head clockwise when the sensing means is deflected said opposite way.

18. The apparatus dened by claim 17 characterized by, the connection 'between said sensing means and said reversible drive means being electrical switch means.

19. Apparatus for wrapping a spiral coil comprising, a coil support, strapping means adjacent to the coil support for providing a strap loop in encircling relation to the coil, tightening means on said strapping means for shrinking the strap loop and .tightening the .strap loop into contact with the outer wrap of the coil, and means attached to the strapping means for rotating the strapping means through 4an arc concentric with the axis of the coil to rotate the entire strap loop while it is in contact with the outer wrap of the coil in a direction to IWrap the coil tight.

References Cited by the Examiner UNITED STATES PATENTS 990,271 4/1911 Hutson et al 100-212 3,019,577 2/ 1962 Slamar et al. 3,044,729 7/ 1962 Prellwitz 242-78.l 3,179,037 4/1965 Cranston et al. 10G- 26 X 3,216,346 11/1965 Cruckshank et al. 100426 X 3,225,683 12/1965 Rhea 100-26 X 3,238,864 3/1966 Patterson 100-3 3,252,408 5/ 1966 Winkler 100-26 FOREIGN PATENTS 497,065 5/ 1930 Germany.

BILLY I. WILHITE, Primary Examiner. 

1. THE METHOD OF WRAPPING A SPIRAL COIL COMPRISING, PROVIDING A STRAP LOOP IN ENCIRCLING RELATION TO THE COIL, SHRINKING THE STRAP LOOP INTO CONTACT WITH THE OUTER WRAP OF THE COIL, MAINTAINING SUCH CONTACT OF THE STRAP LOOP 